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LM317 for Output 4 Volt, 500 mA

Bhavdipsinh Rathod
Expert 2225 points
Other Parts Discussed in Thread: LM317

Dear All,

My Rectified input to LM317 is 12 Volt

I need to get 4 volt output and hence use R1=220 ohm and R2=100 ohm resistor as per reference circuit.

I am getting 4 volt but It is not able to deliver required current(500mA), So which kind of changes I need in my circuit to fulfill requirement.?

Regards

Bhavdipsinh

  • 0
    TI__Mastermind 24975 points
    Bhavdipsinh,

    So is the device holding steady at 4V but limiting the output current?
    Are you sure that the output voltage is changing under load?

    I suspect that maybe the device is going into thermal overload since you are trying to dissipate about 4W.
    What package are you using? You should use a heatsink when trying to dissipate this much power.

    Best,
    Michael
  • 0
    TI__Mastermind 22610 points

    In your case, you are attempting to dissipate 4W in the package ( (12V-4V) x 0.5A )= 4W.

    The TO-263 and TO-220 package ~might~ be able to dissipate this heat with some seriously robust heat sinking, but not so much the SOT-223.